Fluid-driven power plant

ABSTRACT

A fluid-driven power plant for harnessing power from a fluid flowing in a preselected direction has a shaft mounted for rotation about a primary axis substantially perpendicular to the preselected direction and at least three blades attached to the shaft, each of the blades having a frame and at least one panel hingedly attached to the frame, with no more than two of the blades attached to the shaft at any particular axial position along the shaft. In specific embodiments, each of the at least three blades is attached to its frame at a location radially outwardly from the shaft for rotation about an axis substantially parallel to the primary axis. Two of the blades may be attached to the shaft at a first axial location along the shaft and two other blades may be attached to the shaft at a second axial location along the shaft.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application Ser. No. 61/009,232, filed on Dec. 27, 2007, the entire content of which is hereby incorporated by reference for all purposes.

FIELD OF THE INVENTION

The invention is directed to a power plant that harnesses kinetic energy of a moving fluid to rotate a shaft.

BACKGROUND OF THE INVENTION

The technique of harnessing the energy of a moving fluid to rotate a shaft is known. In some power plants, a vertical shaft is rotated by the action of fluid impinging on blades vertically attached to the shaft. Such a device rotates when fluid resistance on one side of the axis of rotation exceeds the fluid resistance on the other side. Fluid resistance of the device increases with exposed blade area. In devices with solid, flat blades, the fluid resistance on each side is equal, so in a uniform fluid flow the device will not spin. Some known designs addressing this issue use blades that automatically change configuration during the rotational cycle to maximize the difference in fluid resistance between opposite sides of the device. One example of this is disclosed in U.S. Pat. No. 17,168 to R. Nutting.

A device having only two such blades situated 180° from each other may become stationary when both blades are parallel to the fluid flow. Devices such as these depend on inertia to carry the blades through this “dead zone” in the cycle, but starting the device from the “dead zone” position or operating the device in slow fluid flow is difficult. To address this issue, some devices have more than two blades so that there is always at least one blade receiving some force from the impinging fluid. Such a device is disclosed in U.S. Pat. No. 611,874 to W. Turner. A disadvantage of this design is that the blades partially shield each other from the impinging fluid, thereby limiting efficiency. For example, in a device with four evenly spaced blades, a blade in a “positive” position may experience the force of the fluid flow across the entire area of its face, and move accordingly, thus rotating the entire device. A blade perpendicular to the fluid flow such that it receives the maximum force from the water may be considered to be in the “positive” position for these purposes. However, once the device rotates even slightly, an adjacent blade begins to shield the first blade, so only a fraction of the available area of the first blade is exposed to the fluid flow. In addition, some devices of this type depend on forces from the fluid itself to automatically change the blade configuration throughout a cycle. In such devices, the shielding effect from adjacent blades may adversely affect this automatic adjustment.

SUMMARY OF THE INVENTION

One embodiment of the invention is a power plant having a vertical shaft with blades hinged to provide maximum exposed blade area while in the positive position. The blades switch automatically to a configuration with minimal exposed blade area when moving against the current to complete a cycle or revolution. In one embodiment, at least three blades are positioned on the shaft such that there are at most two blades at any attachment point on the shaft. In the case of two blades at a single attachment point, the blades are situated 180° from each other. Having only single blades or pairs of blades at each attachment point ensures that each blade receives the full force of the impinging fluid flow since the blades do not shield each other. The other blades are displaced axially along the shaft and are offset from the first group such that the shaft always has at least one blade in a position to receive force from the impinging fluid without a “dead zone.”

Each blade is composed of a frame and at least one pivoting panel. The frame may be attached vertically to the shaft. The panel is attached to the outer vertical edge of the frame with a hinge, allowing the panel to swing up to 180° away from the frame. In the positive position, the panel is fully closed such that the force of the impinging fluid holds the panel flush against the frame. As the blade moves with the fluid flow and the shaft rotates, the inside edge of the panel catches the fluid flow, which swings the panel away from the frame. By the time the blade moves 90° from the positive position, the panel has moved 180° away from the frame under the influence of the fluid and is then parallel to the fluid flow. The panel stays parallel to the fluid flow until the blade points directly upstream. At this time, the panel is once again flush against the frame and remains in this configuration by the force of the impinging fluid while the power plant moves through the positive position of the panel. The freely-swinging panel allows for significantly less drag as the blade moves upstream to complete a given cycle (or revolution) since the fluid resistance comes only from the frame which has a significantly smaller area than the panel. The large difference in fluid resistance between panels on opposite sides of the device greatly increases the efficiency of the apparatus.

More specifically, a fluid-driven power plant according to the invention for harnessing power from a fluid flowing in a preselected direction has a shaft mounted for rotation about a primary axis substantially perpendicular to the preselected direction and at least three blades attached to the shaft, each of the blades having a frame and at least one panel hingedly attached to the frame, with no more than two of the blades attached to the shaft at any particular axial position along the shaft. In specific embodiments, each of the at least three blades is attached to its frame at a location radially outwardly from the shaft for ratation about an axis substantially parallel to the primary axis. Two of the blades may be attached to the shaft at a first axial location along the shaft and two other blades may be attached to the shaft at a second axial location along the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a fluid-driven power plant constructed according to one embodiment of the invention.

FIG. 2 is a top plan view of one embodiment of the fluid-driven power plant of FIG. 1.

FIG. 3 is an isometric view of a fluid-driven power plant constructed according to another embodiment of the invention including a cage.

FIG. 4 is an isometric view of a fluid-driven power plant constructed according to yet another embodiment of the invention including a coupling mechanism for the center shaft.

FIG. 4 a is a fragmentary view of a power take-off structure constructed according to an embodiment of the invention for generating electricity from the fluid-driven power plant of the invention.

FIG. 4 b is a fragmentary view of a power take-off structure constructed according to another embodiment of the invention for powering a reciprocating pump using the fluid-driven power plant of the invention.

FIG. 5 is an isometric view of a fluid-driven power plant constructed according to still another embodiment of the invention including a coupling mechanism for the center shaft and a linkage mechanism on the cage.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a power plant for harnessing the energy of a moving fluid to rotate a shaft, the device having high efficiency and a simple design. As complicated devices have more opportunities for failure, a simple design is especially advantageous for applications such as fluid-driven power plants, where the blades may be difficult to access for repair. Furthermore, any downtime in operation affects the operability of other devices that depend on the power plant for energy.

One embodiment of the invention uses water as the driving fluid. Moving water naturally occurs in many forms, including ocean currents, ocean waves, stream currents and tidal flows. Harnessing the energy in moving water is an efficient and environmentally-sustainable method of generating power. Other driving fluids include air streams such as wind, or water jets in air such as waterfalls or blowholes.

The rotating shaft of the power plant may be connected to any of a variety of different devices to harness the kinetic energy of the fluid flow. For example, connecting the power plant to a generator or alternator converts the rotational energy of the shaft into electricity. Coupling the shaft to a mechanical device using gears or belts harnesses the kinetic energy to drive the device. Attaching a reciprocating pump to transport a fluid against gravity converts the kinetic energy into potential energy. Because the power output may be adjusted by changing the number and size of the blades, a fluid-driven power plant such as the present invention is adaptable to a wide variety of applications.

Referring now specifically to FIGS. 1 and 2, in one embodiment of the invention a plurality of frames 12 are attached to a center shaft 10 having a primary axis of rotation 10 a. The frames 12 and the shaft 10 may be vertical, as illustrated in the drawing figures, or may be arranged in any other suitable configuration. The frame 12 is thin enough to minimize surface area yet thick enough to be rigid and maintain its shape under the force of a fluid stream. Panels 14 are attached to the outer vertical edge of the frames 12 by hinges 16, thus forming the blades 18. The hinge 16 of each blade 18 may be substantially parallel to the primary axis of rotation 10 a, permitting the fluid 20 to push the panel 14 open and shut with respect to the frame 12, as described in more detail below. The panel 14 and the frame 12 are appropriately sized such that the panel 14, when forced against the frame 12, will be held flush against the frame 12 and will not push beyond it. For the sake of clarity, assume the device is designed to turn clockwise when viewed from above as shown in FIG. 2. The fluid 20 flows from the bottom to the top of FIG. 2. In the 12 o'clock position, the panel 14 is flush against the frame 12 and the blade 18 points upstream. As the shaft rotates clockwise, the force of the impinging fluid 20 holds the panel 14 flush against the frame 12. The greatest blade area is exposed to the fluid flow 20 at 9 o'clock, which is considered the fully positive position of the blade 18. As the blade 18 moves past the 9 o'clock position, the radially inner edge of the panel 14 catches the fluid flow 20, causing the panel 14 to swing away from the frame 12. By the time the blade 18 moves past the 12 o'clock position, the panel 14 is 180° from the frame 12 and both point directly downstream. The panel 14 continues to point downstream, parallel to the fluid flow 20, throughout the second half of the cycle (or rotation), from the 12 o'clock to the 6 o'clock position. Since only the frame 12 has a perpendicular component with respect to the fluid flow 20 in the second half cycle, the area of the blade 18 exposed to the impinging fluid 20 is minimized. This maximizes the difference in fluid resistance between the two sides of the device, thereby maximizing the torque applied to the central shaft 10.

The plurality of blades 18 are divided into groups 22 of one or two blades each, with only one group 22 being attached to any one vertical (or axial) section of the shaft 10. In the case of 2 blades 18 per group 22, the blades 18 are displaced 180° apart about the primary axis of the shaft 10. Each subsequent group 18 is attached to a different vertical (or axial) position on the shaft 10, and is offset angularly from at least one other group 18. When considering all of the blades 18, the largest gap between any two blades 18 rotating about the axis 10 should be less than 180°. This requires a minimum of 3 blades 18 in at least 2 vertically-stacked groups 22. In this embodiment, no blade 18 is shielded by another and the device as a whole then does not have a “dead zone.” In one particular embodiment, the blades 18 of one group 22 may be displaced 90 degrees from the blades 18 of an adjoining group 22, as illustrated in FIG. 2.

Radial symmetry allows the device to operate in the same manner regardless of the direction of fluid flow 20, as long as the fluid flow is substantially perpendicular to the primary axis 10 a of the shaft 10. For example, if the device is situated below the surface of the ocean in a location to take advantage of wave energy, the device spins in a clockwise direction when the wave comes in to shore, as well as when the wave retreats. Because the change in configuration of the blade 18 is determined by the fluid forces on the panel 14, the device adjusts automatically to changes in the direction of the fluid flow 20.

The panels 14 may be made of any rigid or semi-rigid material such as wood, metal, or plastic. A non-corroding material, stainless steel for example, is best for salt water applications. The panel 14 may be solid, or may contain one or more hinges to create a flexible structure. The pivot point hinge 16 may be at the outer edge of the blade 18, or may be located anywhere along the length of the blade 18, as long as that location is radially outwardly of the primary axis 10 a of the shaft 10. The blade 18 may also have multiple panels 14 that behave in the same or similar manner as a larger single panel 14.

Referring to FIG. 3, in another embodiment the shaft 10 and attached blades 18 may be encased within a cage 24. The cage 24 serves as a mount to hold the device stationary in the fluid flow 20, thereby increasing efficiency. The cage 24 also protects wildlife from the moving blades 18 of the device and prevents debris from becoming entangled in the blades 18.

Referring to FIGS. 4 and 5, another embodiment of the invention has a modular design that allows for building a custom power plant based on the height of the fluid flow and the space available. This modular design allows a manufacturer to produce and stock a single apparatus containing a set number of blade groups 22 (typically two groups) on a center shaft 10. Each apparatus can then be complete as a stand-alone system. The shaft 10 has couplings 26 on each end to allow for stacking of one such apparatus on top of another with their center shafts 10 coupled together. The stacked structure thus rotates about a common axis 10 a. A power plant can therefore be customized in length and power output simply by designating the number of apparatuses to be stacked together. Each apparatus can also be encased within a cage 24, and the cages can have cage linkage mechanisms 28 to better secure the apparatuses to each other and provide additional structural support.

Thus, the disclosed structure can be configured to take full advantage of the water flow available. If a river, creek, aqueduct or other current is ten (10) feet deep, then five (5) rows of two (2) foot tall panels could be interconnected using the couplings 26 and the cage linkage mechanisms 28 to fully utilize the available water flow. A single generator, alternator, pump or other mechanism can then be positioned at one end of the shaft, typically the upper end, to convert the kinetic energy of the water flow to electricity or other suitable form of energy, as set forth in FIGS. 4 a and 4 b. If a body of water is twenty (20) feet deep, twice as many rows of panels can be used to take full advantage of the flow. In designing a system of this type, however, it is important to consider the large forces involved. If five rows of panels 26×13 inches (or 2.35 square feet) each are placed in an apparatus five rows high to harness energy from a ten (10) foot deep flow of water, 11.75 square feet of panels would be resisting the water flow. At 64 pounds per cubic foot of water, that equates to approximately 752 pounds of water acting on the panels. Depending on the rate of water flow, the forces on the shaft 10 can be extremely high. If the flow of water is twenty (20) feet deep, another five rows of panel could be added to double these figures.

Referring now to FIG. 4 a, a power take-off structure 30 may be mounted to the upper end of the apparatus to convert rotation of the shaft 10 to electrical energy through an alternator or other electricity-generating device 32. The alternator 32 is mounted to a framework 34 that may be rigidly attached to the cage 24 of FIG. 5. The alternator is driven by an extension 36 of the shaft 10 acting through a pulley 38 and a belt or other suitable force transmission member 40. The shaft extension 36 is connected to the shaft 10 by the coupler 26.

Alternatively, as illustrated in FIG. 4 b, power from the shaft 10 is harnessed by a reciprocating power take-off structure 42 mounted to the cage 24 of FIG. 5. The structure 42 has a reciprocating pump 44 operated by an arm 46 that is driven by a drive disk 48 mounted for rotation with the shaft 10. The arm 46 is connected to the drive disk 48 at a point displaced from the axis 10 a of the shaft 10, causing the disk to drive the arm for substantially reciprocal motion in the manner of a crank. In other embodiments, different forms of known mechanical linkage can be provided for connecting a rotating or reciprocating mechanism to the shaft 10.

In another embodiment, the device is tilted slightly away from the primary direction of the fluid flow 20. This takes advantage of gravity to assist in keeping the panel 14 flush against the frame 12 from 6 o'clock to 12 o'clock in the first half rotation of the device. This is particularly helpful in slow fluid flow conditions where the panels 14 might otherwise have a chance to drift open during this portion of the cycle.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiments of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant art in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention. For example, the disclosed power plant may rotate about a non-vertical axis, if desired, and the rotatable blades may be mounted differently than disclosed, without deviating from the scope of the invention. Likewise, the number and arrangement of the blades, frames and coupling mechanisms may vary. 

1. A fluid-driven power plant for harnessing power from a fluid flowing in a preselected direction, comprising: a shaft mounted for rotation about a primary axis substantially perpendicular to the preselected direction; at least three blades attached to the center shaft, each of the blades comprising a frame and at least one panel hingedly attached to the frame; wherein no more than two of the blades are attached to the shaft at any axial position along the shaft; and a structure for connecting to the center shaft.
 2. The fluid-driven power plant of claim 1 wherein each of the at least three blades is attached to its frame at a location radially outwardly from the shaft for rotation about an axis substantially parallel to the primary axis.
 3. The fluid-driven power plant of claim 2 further comprising at least four of the blades, two of the blades being attached to the shaft at a first axial location along the shaft; and two of the blades being attached to the shaft at a second axial location along the shaft.
 4. The fluid-driven power plant of claim 3 wherein the two blades attached to the shaft at the first axial location are displaced 180 degrees from one another about the shaft.
 5. The fluid-driven power plant of claim 4 wherein the two blades attached to the shaft at the second axial location are displaced 180 degrees from one another about the shaft and are displaced 90 degrees from the respective blades attached to the shaft at the first axial location.
 6. The fluid-driven power plant of claim 1 further comprising a coupling mechanism on the shaft and configured to couple more than one fluid-driven power plant for common rotation.
 7. The fluid-driven power plant of claim 6 wherein the coupling mechanism is configured to stack a plurality of fluid-driven power plants for rotation together about the primary axis.
 8. The fluid-driven power plant of claim 1 further comprising a cage supporting the fluid-driven power plant.
 9. The fluid-driven power plant of claim 8 further comprising a cage linkage mechanism configured to connect the cage of the fluid-driven power plant to the cage of another fluid-driven power plant.
 10. The fluid-driven power plant of claim 1 wherein the primary axis of the fluid-driven power plant is tilted away from the preselected direction of fluid flow. 